The present invention relates to a process for the production of hydrocarbon products from a methane comprising feed by means of a Fischer-Tropsch process.
US-A-2007/0004809 discloses a process for producing synthesis gas blends which may be used as feed for a Fischer-Tropsch conversion process. In the process according to US-A-2007/0004809 the synthesis gas blend is prepared by mixing a syngas effluent stream from a steam reforming step with a syngas effluent from an oxygen-blown reforming step. The syngas effluent from the steam reforming step is compressed to a pressure substantially equal to that of the syngas effluent from the oxygen-blown reforming step before both syngas effluents are mixed into the synthesis gas blend that could be used as a feed to a Fischer-Tropsch conversion process. The H2/CO molar ratio of the synthesis gas blend formed is higher than 1.9.
WO-A-2004/041716 describes a process wherein a synthesis gas having a hydrogen to carbon monoxide molar ratio of about 2.04 is prepared in the illustrating examples starting from a natural gas feed by means of a so-called heat exchange steam reforming process. The heat exchange reforming process (HER Process) as disclosed includes an autothermal reformer (ATR) unit and a heat exchange reformer (HER) unit operated in combination. To both reformers a natural gas feed is supplied, although the bulk of the feed is directed to the HER tubeside, where the steam reforming reaction takes place. The partially reformed syngas effluent of the HER unit and the small portion of fresh feed are combined and fed to the ATR unit. The hot effluent of the ATR unit is in turn used to provide the heat of reaction in the HER unit by means of indirect heat exchange. The synthesis gas is used as feed to a Fischer-Tropsch synthesis step to obtain a hydrocarbon product and a residual tail gas. The residual tail gas is recycled to the ATR unit in this process after compressing to the ATR operating pressure.
The heat exchange reforming process is attractive because it has a high efficiency resulting in better conversion, lower oxygen usage and lower CO2 emmissions in comparison with conventional steam reforming processes such as auto-thermal reforming. A disadvantage of the process of WO-A-2004/041716 is that the level of inerts in the synthesis gas is relatively high. Applicants found that in a Fischer-Tropsch synthesis step using one or more fixed catalysts beds, higher levels of inerts is detrimental for the selectivity to useful products of the Fischer-Tropsch conversion. The net result is that a HER process in conjunction with fixed bed Fischer Tropsch synthesis is less attractive since poorer conversion to useful products is achieved in the synthesis stage.